Logo
FULL SITE MENU

140 johnson

S

splitshot

New member
i have a 1977 Johnson 140 hp m

i have a 1977 Johnson 140 hp motor...its on a hydra sports bass boat and i can only get about 3000 rpms out of it i have one cylinder at 95 lbs and the other 3 are at 115 i know this aint the best compression but surely it wouldnt make that much of a difference in the rpms ?? the timming has been checked...the prop is a 13-1/4-17 is the numbers on it...now i need to know what else i can try...thanks
 
"Pull the bypass covers (

"Pull the bypass covers ( 4 of them ) and inspect the pistons and rings , rings are often broken on these models."
 
Just took the boat out with me

Just took the boat out with me and no gear in the boat it would do about 38 mph and 3200 rpm...but the weird thing is i can put it in neutral and it will rev to 5000 rpm i only did this once in the river i dont like doing it but i wanted to see if the motor would atleast rev that high w/o a load
 
"Revving a motor in nuetral pr

"Revving a motor in nuetral proves nothing ---absolutely NOTHING, since there is no load on the motor.The covers are on the side of the motor ---easy to find."
 
"hey jason...Try this...next t

"hey jason...Try this...next time out, when you reach top RPM, pump the primer bulb up hard and hold it...if the engine picks up speed, the high speed jets are dirty and need a carb overhaul..."
 
Well hate to say it but it has

Well hate to say it but it has a broken ring and i guess the guy before me removed the broken piece because there was silicone instead of a gasket on the bypass cover..just out of curiousity what makes them break ???
 
Welcome to the outboard motor

Welcome to the outboard motor trouble shooting club.Give yourself a pat on the back for following some WORLDCLASS ADVICE------enuff said.
 
"77-78 140 has been THE most o

"77-78 140 has been THE most overhauled eng i have ever done....it was very due for an overhaul,even if it had been done 15 yrs ago,would be my guess...broken rings,on these models,was due to high ring pistons,and improperly drilled pistons ring pin holes...the pin dropped down into the piston,allowing the ring to spin and catch on finger ports....this engine,is an excellent overhauler...as long as--lower unit is good,tnt unit in good shape...now days,..u can get a newer engine,say late 80's or 90's for what it would take to do the overhaul PROPERLY....be VERY aware...of the 'short overhaul' fixes,many do...fix the immediate problem and kick it out the door...a quality,professional overhaul,is not cheap,but 1/3 the cost of new eng or so.."
 
well i am still debating on th

well i am still debating on the overhaul but i am in search of an inside micrometer to check the cylinder to see if needs to be bored...does anybody know where i can get one online...nobody local has one or can get one...thanks
 
You just need to find a machin

You just need to find a machineshop/ garage / that has telescopic gauges and a 3-4" micrometer.Should not be hard.The type of piston rings on that motor have an angle on them and it means as the rings wear and move out the side clearance increases. At 5000RPM the rings start to flutter and break.This is a VERY COMMON fault.
 
Well i'm pulling it apart.

Well i'm pulling it apart...is it possible to remove the main bearring/crank case cover off with the power head still on the motor ?? it acts like it is stuck on the dial pins maybe they have to be driven out ?? also the bottom of the hood/cowling is still on the motor will i have to remove it also ?? thanks for any help
 
"Jason , you are going about t

"Jason , you are going about this the wrong way.----stop using a hammer and get a factory manual."
 
"back to one of your other pos

"back to one of your other posts...u need an overhaul....complete tear down,re-bore.hone as necc inst new pistons/parts where needed...dont forget to do the carbs,during this time...if boring,u will need larger HS jets.ALWAYS,inst a new water pump/thermos, during overhaul."
 
Back
Top